Many genetic and environmental diseases result from defective protein folding within the secretory pathway. Aberrantly folded proteins are recognized by the cellular surveillance machinery and retained within the endoplasmic reticulum (ER). Under conditions of malfolded protein accumulation, the cell activates the Unfolded Protein Response (UPR) to clear the malfolded proteins and, if unsuccessful, initiates a cell death response. The proposed studies will identify and characterize drug-like small molecular probes that specifically inhibit the apoptotic arm of the UPR. These compounds will have potential therapeutic application to diverse disease states. The proposed studies will test the hypothesis that reversible inhibition of the UPR death program mediated by CHOP will be an effective strategy to facilitate recovery from pathophysiological stress in diseases characterized by chronic ER stress and protein misfolding. In preliminary studies we have employed complementary high throughput cell-based assays and identified small molecule inhibitors of pro-apoptotic CHOP and enhancers of the adaptive IRE1-XBP1 axis. We propose to extend these initial screens by interrogating larger more diverse chemical collections in collaboration with the Molecular Libraries Screening Centers initiative. Biochemical and genetic approaches will validate the ability of lead compounds to modulate specific UPR subpathways and to identify their molecular targets and mechanism(s) of action. Synthetic chemistry will determine structure activity relationships in search for compounds with higher affinity and specificity. Lead compounds will be tested for their ability to facilitate proper protein folding and limit pathological UPR responses in cell -based assays. Most promising candidates will be evaluated in vivo in several physiologically relevant model systems of human protein misfolding diseases including diabetes, hemophilia, lysosomal storage diseases, and a1-antitrypsin deficiency. The long-term objective of the proposed studies is to identify novel small molecule inhibitors of the UPR death response and characterize their potential as therapeutic agents for treating diseases caused by aberrant protein folding and/or trafficking. Small molecule UPR agonists/antagonists identified through the proposed studies will provide a convenient cost-effective means of treating patients suffering from diseases for which therapies are limited to minimally effective gene therapy or extensive costly enzyme replacement therapies. [unreadable] [unreadable] [unreadable]